The effects of nucleotides and potassium channel openers on the SUR2A/Kir6.2 complex K+ channel expressed in a mammalian cell line, HEK293T cells.
The effects of potassium channel opening drugs and intracellular nucleotides on the ATP-sensitive K+ (KATP) channel composed of SUR2A and Kir6.2 in HEK293T cells were examined using the patch-clamp technique. The SUR2A/Kir6.2 channel was activated effectively by pinacidil, marginally by nicorandil but not by diazoxide. The pinacidil-activated channel currents were inhibited by glibenclamide with a Ki value of 160 nM. Upon formation of inside-out (I-O) patches, spontaneous openings of the channels appeared, which were inhibited by intracellular ATP (ATPi) equipotently in the presence and in the absence of intracellular Mg2+ (Mg2+i). The channel activity ran-down gradually in I-O patches. The run-down channels could be reactivated by ATPi only in the presence of Mg2+i. Uridine 5'-diphosphate (UDP) antagonized the ATPi-mediated inhibition of the channel activity before run-down. After run-down, UDP activated the channel without antagonizing ATPi-mediated channel inhibition. Thus, the SUR2A/Kir6.2 reproduced the major properties of the native cardiac KATP channel well in terms of nucleotide regulation and pharmacology, and therefore can be a useful tool with which to elucidate the molecular mechanisms characterizing the KATP channel.
Okuyama
Y
Y
Department of Pharmacology II, Faculty of Medicine, Osaka University, 2-2, Yamadaoka, Suita, Osaka 565, Japan.
Yamada
M
M
Kondo
C
C
Satoh
E
E
Isomoto
S
S
Shindo
T
T
Horio
Y
Y
Kitakaze
M
M
Hori
M
M
Kurachi
Y
Y
D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D003981:Diazoxide / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009536:Niacinamide / Q000031:analogs & derivatives / Q000494:pharmacology; D020108:Nicorandil; D018408:Patch-Clamp Techniques; D020110:Pinacidil; D015221:Potassium Channels / Q000096:biosynthesis / Q000187:drug effects*; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug / Q000096:biosynthesis / Q000187:drug effects*; D064233:Sulfonylurea Receptors; D014530:Uridine Diphosphate / Q000494:pharmacology*
C577510:ABCC9 protein, human; D018528:ATP-Binding Cassette Transporters; D006146:Guanidines; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D009536:Niacinamide; D020108:Nicorandil; D014530:Uridine Diphosphate; D020110:Pinacidil; D000255:Adenosine Triphosphate; D003981:Diazoxide